bug: aria-hidden=true should be removed

[titanism]

This line needs to be removed:

markdown-it-github-headings/index.js

Line 62 in d4c008d

linkOpen.attrSet('aria-hidden', 'true')

Note that you already have aria-hidden=true on the SVG, which should suffice.

Google's PageSpeed Insights deems this current behavior negatively.

[titanism]

Someone should probably also notify GitHub support of this since this is mirrored from them.